The 1991 Cantabrian parliamentary election was held on Sunday, 26 May 1991, to elect the 3rd Regional Assembly of Cantabria, the regional legislature of the Spanish autonomous community of Cantabria. All 39 seats in the Regional Assembly were up for election. The election was held simultaneously with regional elections in 12 other autonomous communities and local elections all throughout Spain.
The Spanish Socialist Workers' Party (PSOE) under incumbent President Jaime Blanco went on to win its first and only regional election in Cantabria. Juan Hormaechea's Union for the Progress of Cantabria (UPCA), a split from the People's Party (PP), won 15 seats and 33% of the vote, with the PP vote collapsing to 6 seats and 14% of the vote as a result. The Regionalist Party of Cantabria (PRC) suffered from the UPCA's surge and returned to its 1983 results, while the Democratic and Social Centre did not reach the required 5% threshold and was expelled from parliament.
Juan Hormaechea managed to get re-elected as regional President thanks to a UPCA-PP agreement. He had been forced to resign in late 1990, after a no-confidence motion was passed against him by an alliance of PSOE, PP, PRC and CDS.
The number of seats in the Regional Assembly of Cantabria was set to a fixed-number of 39. All Assembly members were elected in a single multi-member district, consisting of the Community's territory (the province of Cantabria), using the D'Hondt method and a closed-list proportional representation system.
Voting was on the basis of universal suffrage in a secret ballot. Only lists polling above 5% of valid votes in all of the community (which include blank ballots—for none of the above) were entitled to enter the seat distribution.
The 1987 election had seen AP candidate Juan Hormaechea win the election with 19 out of 39 seats, 1 short for the absolute majority. Hormaechea, who had been Mayor of Santander between 1974 and 1987 and stood as an independent within AP, was elected as President of Cantabria thanks to the abstention vote of the CDS two deputies.
However, from the beginning Hormaechea's tenure as regional President was controversial. Shortly after being elected, in August 1987, Hormaechea announced "difficulties" in forming a regional government, claiming pressures from AP to force him to name prominent party members as regional ministers, accusing AP of "seeking to create wealth for themselves instead of wanting to serve the region" and threatening to resign from his office. The government crisis was temporarily solved with the naming of three independents and four AP members as regional ministers.
Hormaechea would star another incidents throughout the legislature, including insults to other parties' deputies, accusations to the Assembly Speaker Eduardo Obregón (PSOE) of official misconduct (which resulted in a legal complaint against Hormaechea), as well as accusations from the three opposition parties (PSOE, PRC and CDS) of a continued disregard for the regional chamber. Hormaechea was also accused of political misconduct, such as extortioning other deputies in exchange of their votes, bribing MPs from other parties, as well as influence peddling favoring family members and physically attacking a PSOE senator.
Further, in late 1989, a controversy arose after Hormaechea declared he was not supporting the People's Party, successor party to AP, for that year's general election. From that point, the deteriorating relationship between the PP and Hormaechea as a result of the latter's personalism and marginalization of the party's structure in the region triggered a political crisis. Hormaechea's insults to party leaders in late 1990 motivated the PP's decision not to choose him as candidate for the incoming 1991 election, as well as the party presenting a motion of censure on Hormaechea to remove him from the regional government, with the support from the PSOE, PRC and CDS, electing PSOE leader Jaime Blanco as the head of a coalition administration for the remainder of the legislature. This caused a split within the regional PP, with 12 deputies supporting Hormaechea and 7 supporting the no-confidence motion against him. Hormaechea's grouping went on to form a separate party, the Union for the Progress of Cantabria (UPCA), to stand for the 1991 election.
The unveiling of irregularities within the finances of Hormaechea's government conducted by Blanco's coalition government marked the electoral campaign into the 1991 election. Hormaechea's management of the regional budget had left a public debt worth of 80,000 million pesetas, while auditors discovered spenditures during the 1987-1990 period that were difficult to justify, with evidence pointing to embezzlement during Hormaechea's tenure.
The Spanish Socialist Workers' Party (PSOE) tried to benefit from the split in the centre-right vote, with former Deputy Prime Minister Alfonso Guerra asking conservative voters to vote the PSOE "for this time", reminding the chaotic political situation of the community as a result of the infighting between former President Juan Hormaechea and the People's Party leadership.
Poll results are listed in the table below in reverse chronological order, showing the most recent first. The highest percentage figure in each polling survey is displayed in bold, and the background shaded in the leading party's colour. In the instance that there is a tie, then no figure is shaded. The lead column on the right shows the percentage-point difference between the two parties with the highest figures. Poll results use the date the survey's fieldwork was done, as opposed to the date of publication. However, if such date is unknown, the date of publication will be given instead.
Opinion polls showing seat projections are displayed in the table below. The highest seat figures in each polling survey have their background shaded in the leading party's colour. In the instance that there is a tie, then no figure is shaded. 20 seats were required for an absolute majority in the Regional Assembly of Cantabria.